Indiana currently has two reservoirs of rabies virus, skunks and bats. In the past 5 years, bats have represented 91% of the animals found rabies positive by the Indiana State Department of Health (ISDH) Rabies Laboratory. In the past 10 years, bats have represented 96% of the rabid animals submitted to the laboratory, with the only other rabies positive animals being skunks (6) and horses (1).

In 1999, the Laboratory tested 1,961 animals for rabies. The most frequently tested animals were dogs (717), cats (599), bats (241), and raccoons (179). These species represented 79% of the animals submitted. The other 21% of animals were from 44 other species with 1 to 29 animals per species submitted to the lab for analysis. Counties of origin for bats identified as rabid in 1999 are shown in Figure 1.

Bats submitted to the ISDH Rabies Laboratory are identified by species. In 1999, the identified species and the number of rabies positive bats were Eastern Pipistrella (2), Little Brown (2), Red (6), Hoary (2), and Big Brown (2). Virus variant identification was accomplished by the Centers for Disease Control and Prevention (CDC). Six rabies virus variants were identified from the 13 submitted samples. The virus variants were similar to the variants associated with the species from which they were isolated in other states. The variant isolated from the Eastern Pipistrella and Little Brown Bat is the variant associated with the majority of human rabies infections acquired in the United States. It is the same variant associated with the last human rabies death in the United States (Virginia in 1998). A history of an animal bite or exposure to bats was never determined for this individual.

The importance of bat rabies must be examined in the context of a national perspective. Since 1990, there have been 21 human deaths due to rabies acquired in the United States. A bat variant rabies virus caused 19 of the deaths. A history of a bite or other contact that could have resulted in rabies transmission was determined for 1 of the 19. As a result, the Advisory Committee on Immunization Practices has made major changes in its recommendations for evaluating contact or potential contact with an untested bat. The current recommendation is that postexposure prophylaxis should be considered when direct contact between a human and a bat has occurred, unless the exposed person can be certain that a bite, scratch, or mucous membrane exposure did not occur. In instances in which a bat is found indoors, postexposure prophylaxis can be considered for persons who were in the same room as the bat and who might be unaware that a bite or direct contact had occurred.  For example, a sleeping person awakens to find a bat in the room or an adult witnesses a bat in the room with a previously unattended child, mentally disabled person, or intoxicated person and rabies cannot be ruled out by testing the bat..

A total of 8,119 animal bites were reported in 1999 for a crude incidence rate of 138/100,000. Animal bites are frequently under reported, especially minor bites that do not require medical attention for wound treatment. Therefore, the information presented should be considered the minimum. Dogs continue to be the number one offender with 6,412 reported bites (79 % of all bites), and cats, the number two offender, had 1,279 reported bites (15.8%). Wild animals that are rabies reservoirs, either in this state or other states, that were reported to have bitten humans in Indiana were bats (41), raccoons (60), foxes (2), skunks (5) and coyotes (2). The remainder of the reported bite incidents (322) were made up of other domestic animals or wild animal species that are rarely, or never, reported as rabid. Five reports of monkey bites were received. In addition to a risk assessment for rabies, monkeys should be identified by species and if the animal is a member of the Macaque family, it should be tested for Herpes B virus. Herpes B virus, when transmitted to humans (approximately 40 known cases), causes a rapidly ascending encephalomyelitis that is fatal to approximately 70% of the cases.

Children under age 15 are the most frequent victims of animal bites. Of the 8,082 animal bites where the victim's age was known, 4,014 (49.6%) were under age 15. Figure 2 illustrates the disproportionate high rates in the younger age groups. The female:male bite victim ratio varies by age group also. The female:male ratio is1:1.04 in the 0-4 age group, 1:1.31 in the 5-9 age group, 1:1.65 in the 10-14 age group, and 1:0.89 in the above 15 age group.

In 66 reported incidents in 1999, circumstances of an animal bite or exposure resulted in a decision to administer postexposure immunization against rabies. The postexposure immunization series consists of an initial dose of human rabies immune globulin and 5 doses of rabies vaccine given on day 0, 3, 7, 14, and 28. Figure 3 presents the number of postexposure treatments required by species.

Rabies vaccination of dogs and cats is the primary barrier to preventing exposure of humans to rabies even when the primary vector of rabies in the area is terrestrial wildlife species such as a skunk or raccoon. From animal bite reports, which indicated the rabies vaccination status (yes, no, unknown) of biting animals, it is noted that 50.4% of dogs, 25.2% of cats, and 11.8% of ferrets had a current rabies vaccination. Indiana State law requires annual rabies vaccination for dogs, cats, and ferrets.

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